Variable valve apparatus

Abstract

A first overlap amount that is an overlap amount of overlap between an intake valve opening timing and an exhaust valve opening timing, is calculated based on rotation speed of an internal combustion engine, load on the engine, and temperature of a working fluid. A second overlap amount that is the overlap amount that is set so that the relative rotation phase of at least one of the intake-side camshaft and the exhaust-side camshaft relative to the rotation phase of the crankshaft is fixed when the engine stops, is calculated based on the temperature of the working fluid. The overlap amount is set to equal to the second overlap amount, if the first overlap amount is larger than the second overlap amount. The overlap amount is set to equal to the first overlap amount, if the first overlap amount is less than or equal to the second overlap amount.

1. A variable valve apparatus comprising:
 a rotation phase variable control portion that includes a vane and changes relative rotation phase of at least one of an intake-side camshaft and an exhaust-side camshaft that rotate to open and close an intake valve and an exhaust valve, respectively, of an internal combustion engine, relative to rotation phase of a crankshaft, according to hydraulic pressure of a working fluid; 
 a lock portion that includes a lock pin that is switchable between being fitted and not being fitted to a lock hole formed in the vane so that the lock pin assumes a lock state of fixing the relative rotation phase of at least one of the intake valve and the exhaust valve by mechanically fixing at least a portion of the rotation phase variable control portion when the internal combustion engine stops, and discontinues the lock state when the internal combustion engine starts; and 
 a control device that includes: 
 a first specific determination portion that sets a first overlap amount that is requested as an overlap amount of overlap between an intake valve opening timing during which the intake valve is open, and an exhaust valve opening timing during which the exhaust valve is open, based on rotation speed of the internal combustion engine, load on the internal combustion engine, and temperature of the working fluid; 
 a second specific determination portion that sets a second overlap amount that is the overlap amount that is set so that the relative rotation phase is fixed when the internal combustion engine stops, based on the temperature of the working fluid; and 
 a control portion that controls the rotation phase variable control portion so that the overlap amount becomes equal to the second overlap amount, if the first overlap amount is larger than the second overlap amount, and that controls the rotation phase variable control portion so that the overlap amount becomes equal to the first overlap amount, if the first overlap amount is less than or equal to the second overlap amount. 
 
     
     
       2. The variable valve apparatus according to  claim 1 , wherein the first overlap amount is smaller if the temperature of the working fluid is higher. 
     
     
       3. The variable valve apparatus according to  claim 1 , wherein the second overlap amount is larger if the temperature of the working fluid is higher. 
     
     
       4. The variable valve apparatus according to  claim 1 , further comprising a correction portion that corrects the second overlap amount so that the second overlap amount is smaller if speed of a vehicle that is supplied with power from the internal combustion engine is lower. 
     
     
       5. The variable valve apparatus according to  claim 1 , wherein:
 the rotation phase variable control portion is connected to the intake-side camshaft so as to change the relative rotation phase of at least the intake-side camshaft relative to the rotation phase of the crankshaft, according to the hydraulic pressure of the working fluid; and 
 the control portion controls the rotation phase variable control portion so that the intake valve opening timing is changed. 
 
     
     
       6. The variable valve apparatus according to  claim 5 , wherein if the first overlap amount is larger than the second overlap amount, the control portion controls the rotation phase variable control portion so that the overlap amount is made equal to the second overlap amount by advancing the intake valve opening timing. 
     
     
       7. The variable valve apparatus according to  claim 1 , wherein:
 the rotation phase variable control portion is connected to the exhaust-side camshaft so as to change at least the relative rotation phase of the exhaust-side camshaft relative to the rotation phase of the crankshaft, according to the hydraulic pressure of the working fluid; and 
 the control portion controls the rotation phase variable control portion so as to change the exhaust valve opening timing. 
 
     
     
       8. The variable valve apparatus according to  claim 7 , wherein if the first overlap amount is less than or equal to the second overlap amount, the control portion controls the rotation phase variable control portion so that the overlap amount is made equal to the first overlap amount by retarding the exhaust valve opening timing. 
     
     
       9. The variable valve apparatus according to  claim 1 , wherein if the first overlap amount is larger than the second overlap amount, the temperature of the working fluid is lower than or equal to −10° C., and if the first overlap amount is less than or equal to the second overlap amount, the temperature is above −10° C. 
     
     
       10. The variable valve apparatus according to  claim 1 , wherein at least a portion of the rotation phase variable control portion is mechanically fixed by the lock pin fitting to the lock hole. 
     
     
       11. The variable valve apparatus according to  claim 10 , wherein the lock state is a state in which the relative rotation phase of the intake-side camshaft is a phase in which the vane is positioned furthest to a retarded side in a movable range of the vane. 
     
     
       12. The variable valve apparatus according to  claim 1 , wherein the rotation phase variable control portion changes the relative rotation phase via the working fluid. 
     
     
       13. The variable valve apparatus according to  claim 1 , wherein the first overlap amount is an overlap amount that is requested in order to heighten combustion efficiency of the internal combustion engine.